A number of transition metal-containing compounds, both organic and inorganic, are known to be used for treatments for hydrocarbon systems. These compounds may be included within a hydrocarbon system such as a lubricant (e.g. greases, lubricating oils and the like) and hydrocarbon fuels of both the solid and normally liquid type. Such transition metal-containing compounds are effective catalysts for promoting combustion. Further, the components can promote conversion to cohesive films in the case of paints; and with respect to fuels such compounds can improve combustion properties. U.S. Pat. No. 4,505,718 to Dorer disclosed that the inclusion of transition metal salts of an organic acid can give property improving results when included within lubricants and fuels. Specifically, the inclusion of such metal salts into fuels can improve fuel efficiency. Specifically, manganese salt compounds are effective in reducing the combustion temperature of soot in diesel soot traps. However, it was also found that the inclusion of such metal salts into systems such as fuels sometimes causes deleterious as well as beneficial effects. Among the deleterious effects are the promotion of sediment and sludge in that a fuel containing a high concentration of a manganese salt is unstable with respect to oxidation. Sediments and sludges were found to form within such fuels. Accordingly, the use of such metal salts can cause deposits which interfere with the storage and transport of oil by promoting corrosion as well as interfering with pumps, meters and associated equipment. Accordingly, it was suggested within U.S. Pat. No. 4,505,718 to include an ashless dispersant preferably in the form of an acylated nitrogen-containing dispersant in combination with the transition metal salt in an attempt to eliminate the formation of the sediment and sludge.
Prior to the disclosure by U.S. Pat. No. 4,505,718 it had been known to include various types of transition metal salts into hydrocarbon systems such as fuels as disclosed by U.S. Pat. No. 4,162,986 to Alkitis et al. Further the inclusion of acylated nitrogen-containing dispersants into hydrocarbyl systems was previously known as indicated within U.S. Pat. No. 4,000,082. However, prior to the disclosure within the '718 patent the improved results obtained by including the dispersant in combination with the transition metal salt within a fuel composition was not known.
The literature includes literally hundreds of different disclosures of various compounds and compositions which have been found to be useful as used in connection with hydrocarbon systems such as lubricating oils and fuels. (See for example the citation of patents listed in U.S. Pat. No. 4,505,718). One type of compound which is known to be used in connection with certain types of hydrocarbon containing systems is a dimercaptothiadiazole. Such compounds may be included within hydrocarbon systems in order to act as elemental sulfur scavengers as disclosed within U.S. Pat. No. 3,840,549.
Although numerous compounds and compositions are disclosed as being used in connection with hydrocarbon systems such as lubricating oils and fuels, from time to time it is found that particular combinations of these compounds or compositions improves the properties of the resulting products. However, most combinations would tend to result in an undesirable interaction of the components. An example of a desirable combination was discussed above with respect to U.S. Pat. No. 4,505,718 wherein the conventional dispersant was used in connection with the transition metal salt in order to prevent the formation of sediments and sludge. The discovery of the usefulness of such combinations of known components can result in an extremely useful and commercially successful product. The reasons for this include (1) the relatively low cost; and (2) prior acceptability of such compounds and compositions within similar systems. Cost is often a tremendously important factor in that all compounds or compositions included within lubricating oils and fuels must be relatively inexpensive to make it commercially feasible to include the compounds within such hydrocarbon systems. In addition to the compounds and compositions themselves being inexpensive by combining certain ones in certain proportions it may be possible to eliminate the inclusion of other compounds or compositions which were previously required to obtain acceptable performance. This further reduces costs and increases the desirability of using such a combination.
The use of metal salts to improve efficiency was mentioned above with respect to U.S. Pat. No. 4,162,986. More recently such salts were found to be useful in connection with the spontaneous regeneration of a soot trap present in the exhaust system of a diesel engine. Such soot traps may be included in the exhaust system of a diesel engine in order to trap exhaust particulates. A build-up of such particulate material could clog the system and prevent the engine from operating. By including the metal salts in the fuel, the combustion temperature of the soot in the trap is effectively lowered and the trap is spontaneously regenerated and clogging is prevented. However, as the concentration of the metal in the fuel is increased, the oxidative stability of the fuel is decreased. This decreased stability results in the formation of sediments and sludge during storage.